Problem: Evaluate the following expression when $b = 2$ and $a = 2$. $4$ $b$ $ + 8$ $a$ $ + 7$
Answer: Substitute $2$ for ${b}$ and $2$ for ${a}$ $ = 4{(2)} + 8{(2)} + 7 $ $ = 8 + 16 + 7 $ $ = 31$